Inaccuracy in landmark identification is regarded as the most important source of error in cephalometry. Better definition of landmarks should therefore contribute to better clinical decisions and research validity. This study primarily comprised of an ex vivo investigation on 50 extracted lower incisor teeth to determine whether radiopaque markers could be utilised to accurately assess lower incisor inclination. Fifty extracted lower incisor teeth were mounted onto a Perspex sheet. Radiopaque markers, manufactured from 1mm wide strips of lead film from used peri-apical radiographs, were attached to the crowns of the mounted teeth. A lateral cephalometric radiograph was taken in accordance to standard radiographic procedures (radiograph A). This showed the true inclination of the teeth. A second radiograph was taken with the roots obscured (radiograph B). Three observers traced the inclinations of the teeth on radiograph B (from incisor edge through the middle of the labio-lingual crown-root junction). The determination was done on two different occasions and the assessments compared with the true inclination. Comparative statistical analysis was applied to the readings and the results indicated that this method compared favourably with other methods to determine incisor inclination. In addition, clinical application of opaque markers to the teeth of patients demonstrated the following: it indicated exactly which tooth was being assessed, provided clear definition of the anatomical crown in the sagittal plane and served as a constant reference point for clinical, study model and cephalometric measurements. decisions and research validity. Opaque radiographic markers on teeth can contribute to more accurate cephalometric measurements in orthodontics, leading to better diagnoses, treatment planning and research validity. / Thesis (MChD (Orthodontics))--University of Pretoria, 2005. / Orthodontics / unrestricted

Some orthodontics clinicians apply an empirical method to evaluate the anteroposterior inclination of the upper incisor, in order to visually and qualitatively assess its inclination. It consists in projecting the prolongation of the upper incisor’s axis in relation to the cephalometric point Orbitale (Or) without referring to the conventional cephalometric measures related to the upper incisor. However, this method does not have a scientific basis due to the lack of studies conducted to demonstrate it. Aim: To validate the new measurement I-Or as a reliable method to classify the sagittal inclination of the upper incisor. Method: A total of 305 cephalometric radiographs were selected and classified into three incisor groups: proclined, retroclined, and normal. Cephalometric analyses were performed using standard measures of upper incisor inclination such as I/FH angle, I/NA angle, I/SN angle, and I- NA distance (mm). The shortest distance between the extension of the incisor axis with the Golden point (I-Or) was measured and compared with the I/FH measurement (angle), which was considered the conventional standard to determine the classification of the incisor inclination in this study. Results: There was a statistically significant difference in I-Or values between the 3 groups identified by standard measurement I/FH (p<0.001). I-Or cut-off values of incisors having a normal inclination varied between +2 mm and -4 mm. Conclusion: I-Or is a reliable reference to determine the upper incisor’s inclination in 73% of the cases selected in this study. The sagittal position of the maxilla, the deflection of the incisor axis and cephalometric tracing errors would play a major role in the 27% of cases for which the measurement is not reliable. / Certains cliniciens orthodontistes appliquent une méthode empirique d’observation de l’inclinaison antéro postérieure de l’incisive supérieure, afin d’évaluer visuellement et de façon qualitative son inclinaison. Cette méthode consiste à projeter l’axe de l’incisive par rapport au point céphalométrique Orbitale (Or), et ceci, sans avoir recours au tracé céphalométrique incluant les mesures conventionnelles se rapportant à l’incisive supérieure. Or, cette méthode n’a aucun fondement scientifique en raison de l’absence d’études réalisées pour la démontrer. But : Valider la nouvelle mesure I-Or comme une méthode fiable pour classer l'inclinaison sagittale de l'incisive supérieure. Matériel et Méthodes : Un total de 305 radiographies céphalométriques a été sélectionné et classé en trois groupes d’incisives : proclinées, rétroclinées et normales. Les analyses céphalométriques ont été effectuées en utilisant les mesures standards d’inclinaison de l’incisive supérieure telles que I/FH angle, I/NA angle, I/SN angle et la distance I- NA (mm). La plus courte distance entre le prolongement de l’axe de l’incisive avec le point Or (I-Or) a été mesurée et comparée à la mesure I/FH (angle) qui a été considérée le standard conventionnel pour déterminer la classification de l’inclinaison de l’incisive dans cette étude. Résultats : Il y a une différence statistiquement significative des valeurs I-Or entre les 3 groupes identifiés par la mesure standard I/FH (p<0,001). Les valeurs seuils I-Or des incisives à inclinaison normale étaient de +2 mm et de -4 mm. Conclusion : I-Or est une référence fiable pour déterminer l'inclinaison de l'incisive supérieure dans 73% des cas sélectionnés dans cette étude. La position sagittale du maxillaire, la déflexion de l’axe de l’incisive et les erreurs de traçage céphalométrique joueraient un rôle majeur dans les 27% des cas pour lesquels la mesure n’est pas fiable.